This invention relates to an arrangement for silencing the exhaust gases discharged in first and second streams from separate exhaust gas manifolds of a multi-cylinder internal combustion engine, and more particularly, to a silencing arrangement wherein the two streams traverse different but equal lengthed paths before being combined into a single stream.
A multi-cylinder internal combustion engine is equipped with two parallel rows of cylinders with each row typically being on a different side of the engine and an exhaust system for conducting the burned gases from the engine. The exhaust system includes two manifolds each covering a respective row of cylinders and including an exhaust pipe, and a Y-pipe for connecting the exhaust pipes to a common discharge pipe. The exhaust gases are then passed rearwardly to an acoustic muffler for silencing the exhaust gases.
In such arrangement, the engine is symmetrical to the vehicle and the distance between the respective manifolds and the Y-pipe is the same. During engine operation, the exhaust gases are discharged as pressure pulses in a regular but repeating pattern and the peaks of the pulses are distributed, in time, in such a way as to form a smooth pressure wave of uniform amplitude.
In recent vehicle designs, the location of the engine and the transmission as well as required placement of catalytic converters has resulted in the distance that the gas streams must traverse in moving between the two manifolds and the Y-pipe not being the same. If the distance between the respective manifolds and the Y-pipe are not the same, then the two gas streams will arrive at the Y-pipe at a different time. If this happens, the pressure waves can adversely combine to provide irregular pulsations (e.g., points where the pressure is zero or points where the pulses combine). The noise can be unexpectedly high.
An object of this invention is provision of an exhaust system for an internal combustion engine, which can be integrated with an exhaust muffler, that is effective as a sound silencer, decreases the gas velocity, attenuates sound pressure levels and combines separate exhaust gas streams into a single stream of substantially uniform pressure pulses.
Another object of this invention is provision of an equalizer and compact muffler design which contains within a sheet steel cylindrical shell, expansion chambers, resonance chambers, baffles, and perforated tubes whose function is to intermingle and expand the gases to attenuate the exhaust noise.
Commensurate with the design or redesign of a vehicle and the location of its engine and exhaust system is the desire that the mounting not adversely effect the engine performance, be cost effective, and achieve optimal sound attenuation.